It sounds like you need a specialist auto electrician, and it might be worth checking one or two local to you.
If you were near me, I'd happily offer to come over and give a hand, but perhaps the club has someone within reach of Bridgnorth who can offer a hand?
The electrics associated with the wiper motor are not that complex, and are rather prone to failure in old age.
I'd look for answers to the following questions:
1. With the ignition switched on, and the wiper turned on, is the motor turning, even though it isn't moving the wiper arm?
2. Is the wiper motor earthed?
3. With the ignition switched on, and the wiper turned on, does the positive lead to the wiper motor have a current?
If the wiper motor has an effective earth, and there's current on the positive connection to the motor, then the motor has failed and needs replacing.
If there's no effective earth for the wiper motor, then one needs to be added.
@Jayw13702 's suggestion of a faulty wiper relay is a good one, and that is definitely worth getting checked.
I'd encourage you to find someone who can do a VCDS scan for you, since that may well shed some light on the cause of the problem.
Good luck with getting this sorted, it can't be anything too difficult.